“The evidence before our Committee demonstrates that Mr. Park is an honest and exemplary public servant, and your unsubstantiated public attacks against his integrity are a deficient basis on which to justify a subpoena against him,” Cummings wrote with Rep. Gerry Connolly (D-Va.).

Cummings said Issa’s subpoena was “diverting Mr. Park’s energies” from his work and could “seriously impair” the race to repair HealthCare.gov.

“Rather than denigrate Mr. Park’s reputation and impede his time-sensitive work, we request that the Committee accept his reasonable offer to testify before the Committee in December,” Cummings wrote.

Issa subpoenaed Park last week, ordering him to testify Wednesday before the Oversight Committee.

The committee chairman said he offered a handful of opportunities for Park to speak in front of his committee but was continuously rebuffed by the White House, which said Park was too busy to appear.

Issa said Park’s “long history of involvement in the development and rollout of HealthCare.Gov” made his testimony crucial to ensuring the site gets fixed.

“Millions of Americans have lost their health insurance and are rapidly approaching a point where they must begin to prepare for the possibility of having no health insurance,” Issa wrote in his subpoena letter. “They deserve your sworn testimony before their elected representatives about what went wrong.”

Park’s office lashed out after the subpoena was issued.

Donna Pignatelli, the assistant director of the Office of Science and Technology Policy (OSTP), wrote a letter to Issa that said the agency had made numerous attempts to accommodate the chairman’s request for a briefing with Park.

“These efforts to accommodate your interest in hearing from Mr. Park were rebuffed and met instead with a subpoena threat in your letter yesterday,” Pignatelli wrote. “You explained that the Committee feels it has a duty to conduct oversight of the Executive Branch, but conspicuously absent from your letter was any statement or justification that would explain the legislative need to compel Mr. Park to appear next week as opposed to a few weeks from now.”

“OSTP is left to wonder why you would demand Mr. Park appear on November 13, knowing that doing so is more likely to hurt rather than help the goal of fixing the website as soon as possible,” she wrote.

Three technology experts with ties to the White House have created a website called “Let Todd Work” that argues Issa is wasting Park’s time at a critical juncture for HealthCare.gov.

The Obama administration is under intense pressure to fulfill its promise of fixing the broken website by the end of the month.

Cummings on Monday argued that the purported reasoning behind Issa’s subpoena was misleading, and accused him of selectively leaking and misrepresenting internal documents in an effort to score political points.

On Fox News last week, Issa accused Park of “engaging in a pattern of interference and false statements,” saying he had misrepresented website test results that showed how much capacity the site could handle ahead of its launch.

Cummings responded that the Oversight Committee “has obtained absolutely no evidence that Mr. Park has engaged in any pattern of interference during this investigation, and we certainly have identified no evidence that Mr. Park made any ‘false statements’ relating to Healthcare.gov or any other matter.”

Since the federal site went up on Nov. 1, Issa has leaked documents that show the government and contractors were scrambling to make last-minute repairs to the site just as it was going live.

Democrats say those disclosures are meant to embarrass the administration, but Issa and other Republicans say they are conducting legitimate oversight of problems that the White House is trying to hide.